Antimony tallate catalysis of foams prepared from carboxy-containing adduct polyols

ABSTRACT

THE CATALYSIS OR RIGID URETHANE-TYPE FOAMS PREPARED FROM POLYARYLPOLYISOCYANATES AND FREE CARBOXY-CONTAINING ADDUCT POLYOLS IS IMPROVED BY THE USE OF ANTIMONY TALLATE AS THE CATALYST. ANTIMONY TALLATE IS ALSO EXTREMELY EFFECTIVE IN FOAMS CONTAINING AROMATIC CARBOXYLIC ACID DERIVATIVES AS A THIRD PRINCIPAL COMPONENT. THESE FOAMS ARE USEFUL FOR APPLICATIONS REQUIRING GOOD FIRE RESISTANT PROPERTIES.

United States Patent O l 3,813,355 ANTIMONY TALLATE CATALYSIS F FOAMSPREPARED FROM CARBOXY-CONTAINING ADDUCT POLYOLS John K. Allen, Batavia,111., assignor to Standard Oil Company, Chicago, 111. No Drawing. FiledAug. 21, 1972, Ser. No. 282,465 Int. Cl. 008g 22/40, 22/44 U.S. Cl.260-25 AB 2 Claims ABSTRACT OF THE DISCLOSURE The catalysis of rigidurethane-type foams prepared from polyarylpolyisocyanates and freecarboxy-containing adduct polyols is improved by the use of antimonytallate as the catalyst. Antimony tallate is also extremely effective infoams containing aromatic carboxylic acid derivatives as a thirdprincipal component. These foams are useful for applications requiringgood fire resistant properties.

BACKGROUND OF THE INVENTION This invention relates to an improvement inthe catalysis of certain rigid urethane foams which are prepared by thereaction of polyarylpolyisocyanates with carboxycontaining adductpolyols.

The production of rigid urethane-type foams is a well known art withthese foams having a wide variety of industrial and commercialapplications. A primary use of urethane-type rigid foams is as aninsulating material. As an insulator, rigid foams may be shaped intoslabs or sheets of varying thicknesses and placed between walls, inroofs, in floors, and the like. The foams may also be used to makemetal-foam composites which are prepared by foaming the urethane-typematerial so that it is brought in contact with or is confined by metalsheet or metal foil. This type of prefabricated composite may then beused as a structural member for walls, floors, and roofs. These rigidfoams may also be formed into annular or contour shapes which are usefulin insulating pipes and ducts. The rigid foams can also be directlapplied to numerous substrates by spray foaming techniques. These sprayfoam applications are particularly important in such areas as schoolsand warehouses to provide the necessary insulation requirements properfor heating and cooling.

Most conventional urethane foams are 2-component foams. They areproduced by reacting a polyarylpolyisocyanate with a polyfunctionalalcohol or polyol such as the polyether or polyester polyols. Theseconventional urethane foams do not provide the necessary flameresistance, self-extinguishing characteristics and low smoke productiondesirable in many insulating material applications.

Certain modified urethane foam compositions have been developed whichtend to overcome a number of the shortcomings of the conventionalurethane foams. These modified polyurethane foams, which are disclosedin U.S. Pat. 3,637,543 contain a third principal component, an aromaticcarboxylic acid derivative, such as trimellitic anhydride or the acidchloride of trimellitic anhydride.

Both the conventional 2-component urethane foams and the above-mentioned3-component modified urethane foams have more recently been improved bythe replacement of the normal polyfunctional alcohol or polyol componentby adduct polyols containing free carboxyl groups. Thesecarboxy-containing polyols are the half-ester reaction products of (a)polyether polyols and mixtures thereof with (b) anhydrides ofpolyfunctional carboxylic acids such as tetrabromophthalic anhydride andtrimellitic anhydride. These carboxy-containing polyols contain both iceunreacted hydroxyl groups and carboxyl groups. Polyols of this type aredescribed in U.S. Pat. 3,642,646. Certain I i-component modifiedurethane foams containing these polyols are described in British Pat.1,246,732. Rigid urethane-type foams incorporating these freecarboxycontaining adduct polyols possess very good flame resistance,good self-extinguishing characteristics, and produce little smoke whenexposed to flame.

However, foams prepared from these carboxy-containing adduct polyols arenot catalyzed by known urethane foam catalysts as rapidly as foamscontaining conventional polyols. When the rate of catalysis is measuredby the time it takes the foam to rise (rise time) and the time requiredfor the foam to become non-sticky or tack free (tack free time),conventional urethane catalysts do not provide a fast enough reaction topermit the carboxy-containing polyol foams to be used in many of themost desired applications.

In the production of slab or sheet stock, fast catalysis of the foamingreaction is not always required as equipment arrangement and such maypermit foam rise and tack free times up to a few hundred seconds. Manyconventional urethane catalysts, such as tertiary amines and organotincompounds, are adequate for the production of the slab or sheet stockfoam. Among the tertiary amine catalysts suitable for catalyzing thesefoams are triethylamine, triethylenediamine, tetramethylethanediarnine,tetramethylbutanediamine, diethylcyclohexylamine and pyridine. Among thesuitable organo-tin compounds are stannous octoate, dibutyltindilaurate, and particularly dibutyltin diacetate. But, the compoundsfrom these known classes of foam catalysts do not provide sufficientlyfast reaction rates for the production of metal foam composite panels,pipe insulation, and sprayed foams from either 2-component or3-component foams prepared with carboxy-containing adduct polyols.

Another class of catalysts are the antimony carboxylates which can berepresented by the general formula Sb(OOCR) wherein R represents analkyl group. Illustrative of antimony carboxylates include antimontriacetate, antimony tributyrate, and antimony tricaprate. U.S. Pat.3,245,958 broadly teaches the effectiveness of antimony carboxylates ascatalysts in the reaction between isocyanate-containing compounds andactive hydrogencontaining compounds. The patent also teaches the greatercatalytic activity of these compounds over the prior art catalysts inconventional polyurethane foams.

What I have discovered is the outstanding catalytic effectiveness ofantimony tallate in foams prepared with carboxy-containing adductpolyols. While antimony tallate is an antimony carboxylate, it was nottaught in U.S. Pat. 3,245,958. In addition, experiments indicate thatantimony tallate is a poor catalyst for the preparation of conventionalurethane foams from polyarylpolyisocyanates and conventional polyetherpolyols (see Example 1). In those conventional foams it is a much lesseffective catalyst than known amine and tin catalysts such astriethylamine and dibutyltin diacetate.

Thus, it is quite surprising that antimony tallate is such an extremelyeffective catalyst in both 2- and 3-component urethane foams formulatedwith carboxy-containing adduct polyols. In these carboxy-containingpolyol foams, antimony tallate is vastly superior in catalytic activityto the conventional catalysts. For example, in the 3-component foamdescribed in Example 3, the rise and tack free times for foams catalyzedwith 2 g. of antimony tallate are 40 sec. and 106 sec., respectively. Atthe same catalyst level, the values for dibutyltin diacetate are 142sec. and 365 sec. For triethylamine the values are 148 sec. and 252 sec.The effectiveness of antimony tallate is such that it renders foamsprepared from the carboxy-containing This invention relates to a processfor producing a flame-resistant foam composition from the reactionof'(1) a polyarylpolyisocyanate and (2) a carboxy-containing half-esteradduct polyol or mixture of adduct polyols which is prepared by reacting(a) at least one polyether polyol with (b) an anhydride of apolyfunctional carboxylic acid. The improvement in this process is thecatalysis of the foaming reaction with a catalytic amount of antimonytallate. This invention further relates to an improvement in the processfor producing a foam composition containing (1) apolyarylpolyisocyanate, (2) a carboxy-containing adduct polyol, and (3)a polyfunctional aromatic carboxylic acid derivative.

DESCRIPTION OF THE INVENTION Antimony tallate is useful when present inconcentrations of from about 0.25 to about 2.5 weight percent ofstarting materials. The amount of antimony tallate is preferably keptbelow about 1.5 percent. Concentrations high er than these may tend toproduce adverse effects on other foam properties and, of course,increases the cost of the product foam.

The polyols'useful in this invention are a particular class of polyolscontaining both free carboxyl groups and hydroxyl groups. Thesecarboxy-containing adduct polyols may generally be described ashalf-ester reaction products of (a) polyether polyols and mixturesthereof with (b) anhydrides of polyfunctional earboxylic acids.Poly(ethylene glycols) may be reacted with the above components or maybe added after the carboxy-containing polyols have been prepared.

The polyether polyols used in the preparation of the carboxy-containinghalf-ester reaction products include polyethers such as polyoxyalkyleneglycols. These polyethers are obtained by the addition of one or morealkylene oxides, such as ethylene oxide, propylene oxide, and the like,to hydroxy-containing compounds such as ethylene glycol, propyleneglycol, diethylene glycol, dipropylene glycol, and the like; oraliphatic polyols such as pentaerythritol, sucrose, sorbitol,alphamethyl glucoside, trimethyl propane, and the like. Particularlysuitable polyether polyols include the poly(oxypropylene) adducts ofpentaerythritol, sucrose, sorbitol, alphamethyl glucoside, trimethylpropane, and the like.

These polyether polyols may conveniently be blended prior to reaction inorder to maintain a workable viscosity, with poly(ethylene glycols) suchas diethylene glycol, triethylene glycol, tetraethylene glycol or apoly(ethylene glycol) having an average molecular weight in the range offrom about 200 to about 500: A particularly preferred glycol is apoly(ethylene glycol) having an average molecular weight of about 200.When polyol/glycol blends are employed, it is advantageous that theblend comprise from about 90 to about weight percent of the glycol andfrom about 10 to about 90 weight percent of the polyether polyol. Ingeneral, a blend of from about 80 to about weight percent of thexglycoland from about 20 to about 80 weight percent of the polyether polyol issatisfactory. A particularly preferred: composition of the blend is fromabout 60 to about weight-percent of the glycol and from about to about75 weight percent of the polyether polyol.

The above-mentioned poly(ethylene glycols) may also be added to theprior react d ca bonp The anhydrides of polyfunctional carboxylic' acidswhich are suitable for use in, preparing the carboxy-containing polyolsmay be generally described as anhydrides of carboxylic acids containingtwo or more carboxy functions. The carboxylic acids may be eitheraromatic or aliphatic and may contain substituents such as alkyl orhalogen in addition to the carboxy functions. Suitable anhydridesinclude: phthalic anhydride, tetrachlorophthalic anhydride,tetrabromophthalic anhydride, trimellitic anhydride, maleic anhydride,malo'nic anhydride, succinic anhydride, chlorendic anhydride(Diels-Alder reaction product of hexachlorocyclopentadiene and maleicanhydride), bisanhydride of trimellitic anhydride, pyromelleticdianhydride, and benzophenone tetracarboxylic dianhy dride.Tetrabromophthalic anhydride, chlorendic anhydride, and trimelliticanhydride are especially preferred.

To form the carboxy-containing half-ester adduct polyols useful in thisinvention the polyether polyol, mixture of polyether polyols, or thepolyether polyol/poly(ethylene glycol) blend should be combined withfrom about 5 to about 50 weight percent, on a total Weight basis, of theanhydride of the polyfunctional carboxylic acid. A particularlypreferred ratio of components is from 25 to 40 weight percent of theanhydride and from 75 to 6,0 weight percent of the polyether polyol orpolyether polyol/poly(ethylene glycol) mixture.

The adduction reaction is conveniently carried out by combining theanhydrideand polyol constituents in a vessel equipped with a stirringmeans, a thermometer, temperature control means, and nitrogen blanketingmeans. Preferably, the half-ester reaction is carried out in-thepresence of a basic catalyst such as triethylamine. From about 0.05 toabout 2.0 weight percent of the catalyst is a suitable amount. Neitherthe catalyst nor the nitrogen blanketing is necessary to the preparationof the adduct, but both are included in the preferred method ofpreparation.

The carboxy-containing half-ester adduct, is prepared by heating themixture of polyol and anhydride at a temperature from about to 350 F.,preferably-180 to 220 F., for from 1 to 16 hours. The reaction mixtureis heated until the acid number corresponds to that of the half-esterreaction product. Depending upon the particular constituents, this acidnumber may be obtained somewhere in the range of 150 to 300 F. Usually,it is observed around 180 to 220 F. Generally, the mixture is main:tained at the reaction temperature for from about 1 to about 16 hours orlonger. The adduct composition is allowed to cool and is suitable forimmediate use in foam preparation. It is important that the temperatureof the re action remains below the temperature at which the freecarboxyl group, which forms when the hydroxy-containing compounds addsacross the anhydride linkage, will react with the additional hydroxygroups to form a full ester.

Another method by which the polyol adduct composition may be preparedinvolves combining the anhydride of the polyol or polyol blend in avessel, together with a catalyst if desired, and heating the mixturedirectly to between about 200 and 350 F. This temperature is maintainedfor about one hour. The resulting adduct is allowed to cool and is thenready for use.

The polyarylpolyisocyanates useful in this invention are liquidscontaining at least two aromatic rings, each ring being substituted byat least one isocyanato group. The aromatic rings may be suitablyinterconnected by one or more methylene, propylene, carbonyl, sulfoxide,sulfone or ether linkages. Isocyanate-substituted biphenyls are alsosuitable. The aromatic rings of any of the above compounds may beadditionally substituted by ethyl, methyl, or propyl groups. Specificexamples of suitable liquid polyarylpolyisocyanates for use with theinvention include: polymethylene polyphenylisocyanates having from 2 to10 benzene rings and liquid mixtures at room temperature ofpolymethylene polyphenylisocyanate with one or more of the followingpolyarylpolyisocyanates:

4,4 diphenylmethylene diisocyanate; diphenylmethylene 3,3'-diisocynate;diphenyl diisocyanate; diphenylsulfone diisocyanate; diphenylsulfidediisocyanate; diphenyl sulfoxide diisocyanate; and diphenylpropanediisocyanate. Polymethylene polyphenylisocyanates having an averagefunctionality of about 2.1 to 3.5 are particularly suitable isocyanates.

As indicated previously, the foams containing the carboxy-containingadduct polyols may include an aromatic carboxylic acid derivatives as athird principal component. The preesnce of this third component tends toreduce the smoke produced on exposure to flame and helps to improve theflame resistance of the foam. The aromatic carboxylic acid derivativescontemplated for use here are polyfunctional derivatives, having thearomatic nucleus substituted by members selected from the groupconsisting of carboxyl, anhydride or acyl halide. More than one memberof this group may be present on the aromatic nucleus. Other substituentsmay also be present on the aromatic nucleus; for example, alkyl groupscontaining one to four carbon atoms, nitro groups and halide groups.Illustrative aromatic carboxylic acid derivatives are trimellitic acidanhydride, trimellitic acid, double anhydride of trimellitic anhydride,trimellitic acid halide, pyromellitic dianhydride, pyromellitic acid,terephthalic acid, phthalic acid, phthalic anhydride, isophthalic acid,trimesic acid, and benzophenone tetracarboxylic acid or the dianhydrideor acyl halide derivatives thereof.

In addition to the above-described principal or major components, thefoams intended to be used with the catalyst of this invention cancontain other ingredients. Among the ingredients usually added is ablowing agent. The amount of blowing agent combined with the reactantmixture can vary from about 1 to about 25 weight percent. Anadvantageous amount of blowing agent is about to 20 weight percent ofthe foam component mixture.

It is often advantageous to employ additive materials which producecertain effects in the foam composition. One such additive is a siliconesurfacant. Silicones of the type useful in rigid foam preparation aresurface tension depressants. As such, they reduce the energy required toform new surfaces and thus promote bubble formation. Highly effectiveagents will also favor the production of finer, more uniform bubbles andresulting cell structure. The silicones also equalize tensions on thesurface of the bubble, resulting in a foam of increased strength.Silicone surfactants useful in the foams of this invention may begenerally described as siloxane glycol block copolymers with specificgravity in the range 0.5 to 1.5 and viscosity at 25 C. in the range 1 to1000 cps. The amount of surfactants present can vary from about 0.01 toabout 2.0 weight percent of the foam component mixture. An advantageousamount is from about 0.5 to about 1.0 weight percent.

Although they may have serious drawbacks in certain formulations, flameretardants are another type of additive sometimes useful in rigid foamswhich are used for insulation purposes. The principal types of flameretardants are non-reactive solids and liquids. Many of these compoundsare known in the art. Antimony trioxide and halogenatedorgano-phosphorus compounds are examples of these inert flameretardants. An advantageous amount of these fire retardant additives isfrom about 3 to about 6 weight percent of the foam reactant mixture.

Of course, other additives known in the art can be added to the foamsdisclosed herein without departing from the scope of the invention.

Many known methods of foam production can be used to combine the variousingredientsused in the foam. Onemethod-is to combine all the ingredientssimultaneously. This is usually not practical 'as the number ofcomponents to be combined can be quite large. Preferably all of theminor ingredients and the catalyst-and most or all of the blowing agentare premixed with one of the principal components, either thepolyarylpolyisocyanate or the polyol,

before the principal components are combined. Generally it is preferredto combine the catalyst and the other ingredients with the polyolcomponent, although the catalyst and most of the other ingredients canbe combined with the polyarylpolyisocyanate.

With a 2 principal component foam system the formulation usually employsfrom about 0.5 to about 12 equivalents of polyarylpolyisocyanate foreach hydroxy equivalent of the carboxy-containing adduct poly-o1.Advantageously the polyarylpolyisocyanate will be employed in an amountequal to from 0.8 to about 1.5 equivalents for each hydroxy equivalentof adduct polyol.

In the 3-component foam system, the aromatic carboxylic acid derivativecan be rapidly mixed with either the polyarylpolyisocyanate or polyolwith the resulting mixture then being mixed with the remainingcomponent. In another version all three principal components can beadded instantaneously. A preferred method is to prepare apolyarylpolyisocyanate polyfunctional aromatic acid derivative foamprecursor mix and react this with the polyol. The catalyst, blowingagent, and other ingredients are added to these components as describedabove.

In a suitable formulation, the ratio of equivalents of the liquidpolyarylpolyisocyanate to the polyfunctional aromatic carboxylic acidderivative is from 0.6:1.0 to 4.0:1.0 and the ratio of equivalents ofthe adduct polyol, based on hydroxyl, to the polyarylpolyisocyanate andaromatic carboxylic acid derivative is from 0.1:1.0 to 3.0:1.0. In thesecalculations, the anhydride group is assigned a functionality of 1(one). All ratios are calculated using the initial functionality of thestarting materials. In a more preferred formulation, the ratio ofequivalents of the polyisocyanate to the aromatic carboxylic acidderivative is from 1.1:1.0 to 2.2:1.0 and the ratio of equivalents ofthe polyol hydroxyl to the polyisocyanate and the aromatic carboxylicacid derivative is 0.15 :1.0 to 0.9:1.0.

The effectiveness of any particular catalyst is usually determined bymeasuring the time required for the mixed foam components to rise (risetime) and the time required for the foam to become non-sticky (tack freetime). In laboratory work, where relative rise and tack free times areimportant, absolute rise and tack free times are not always measured. Inthe experiments below, the rise time is determined by measuring the time(in seconds) required for the foam to rise to the top of a 12inch highpaper tub. This generally corresponds to about three-fourths of thetotal foam rise. The tack free time is taken to be the time sec.)required for the foam to become non-sticky when contacted With a woodentongue depressor.

The measurement of these times begins at the end of the mixing period.Typically, foam components need to be mixed for from 15 to 30 seconds inorder to develop good foam properties. However, in studies of therelative effectiveness of various catalysts this mixing time wassometimes reduced to as little as 5 seconds in order to permit somemeaningful time differences to be obtained.

Rise and tack free times of a few hundred seconds are generallypermissible in the production of bun stock foam as fast catalysis is notusually necessary. Shorter rise and tack free times are required for theproduction of metal foam composite panels and pipe insulation, and evenshorter times are necessary in spray foam applications.

EXAMPLE 1 Weight (g.) Isocyanate A 146 Polyol B 99 Polyethylene glycol13-200 1 Weight (g.) Silicone surfactant 2 Blowing agent R-ll (CFCI 30Catalyst As below Isocyante A was a polyarylpolyisocyanate with anaverage equivalent weight of 133 and an average functionality of3.1-3.2.

Polyol B was a propylene oxide adduct of pentaerythritol with an averageequivalent weight of 100 and an average functionality of 4.

Polyethylene glycol E-200 was a polyethylene glycol with an averageequivalent weight of 100 and a functionality of 2.

The polyol, polyethylene glycol, surfactant, blowing agent, and catalystwere blended together at room temperature. The isocyanate was added allat once with the mixture being stirred with a high speed blade blenderfor 30 seconds.

TABLE I Mixing Tack Wei ht time Rise free Catalyst g (see) time timeTnethylamme 1 30 106 207 o 2 30 72 129 Dibutyltin cliacetete 1 30 124145 Antimony tallate... 1 3E) 600 600 2 30 117 165 EXAMPLE 2 In thisexample the same catalysts were tested for their effectiveness in a2-component urethane foam prepared with a carboxy-containing half-esteradduct polyol. The data indicates that antimony tallate is anexceptionally fast catalyst for this reaction and that it is vastlysuperior to the conventional amine and tin catalysts in regard to bothfoam rise and foam tack free times.

The foam formulation used in this example was:

Weight (g.) Isoeyanate A 147 Polyol C 167 E-200 l Silicone surfactant 2R-ll 30 Catalyst Varied Isocyanate A was defined in Example 1.

Polyol C is a carboxy-containing adduct polyol prepared by reactingtetrabromophthalic anhydride, a polyethylene glycol, and a propyleneoxide adduct of pentaerythritol with an average equivalent weight of 100and an average functionality of 4. The weight ratio of these reactantswas 2:122.

The components were mixed in the manner described in Example 1 for thetimes indicated below.

The foam formulation used in the experiments of this example was:

Weight (g.)

Isocyanate A 100 Trimellitic anhydride Polyol C 68 E-ZOO 13 Polyol D v20 Silicone surfactant 2 Liquid halogenated organo-phosphorus flameretardant 7 15 R-l 1 40 Catalyst As below Polyol D is a propylene oxideadduct of sucrose with an average equivalent weight of 106 and anaverage functionality of 8.

Components A and C were described above.

A mixture of the isocyanate, trimellitic anhydride, and a portion of theblowing agent-was added to a mixture of Example 3 was repeated usingadditional conventional catalysts and using a different foamformulation. The foam components were combined as in Example 3 and mixedfor 15 sec. The foam formulation used was:

Weight (g) Isocyanate A 100 Trimellitic anhydride 55 Polyol B 11 PolyolE 73 Silicone surfactant 2 Liquid halogenated organo-phosphorus flameretardant 10 Water 0.5 R-ll 30 Catalyst As below Components A and B weredescribed above.

Polyol E is a carboxy-containing half-ester adduct polyol prepared byreacting Polyol D, tetrabromophthalic anhyand a polyethylene glycol inthe weight ratio of TABLE IV TABLE 11 A Tack Weight Mixing Else tree TacPercent ab r agi tfr i Catalyst (g) time time t1me Wei ht Rise 'iree 200F./ (cycles) None 0 30 356 Catalyst (g.) time time 1 hr. in.) 'meniiiifliii 1 so 313 o 115 390 2 309 0.5 35 212 7 "1155 Dibutyltin diacetate1 30 193 1. 0 .55 137 s 483 Antimonyt to. 1 30 53 1.5 42 125 2 513EXAMPLE 3 2 g g 17 391 In this example the catalysts were tested fortheir efmine 2 132 380 1 fectiveness in a 3-component modified urethanefoam pre- 3 pared with a carboxy-containing adduct polyol. The data 4 92325 7 is I as in Table III again indicates that the use of antimonytallate 2 350 15 p 89 in half-ester adduct polyols results in fasterrise and tack I; 375 p i; in) free times than could be obtained via theuse of conveni 17 tional urethane catalysts.

Percent AV is the percentage of volume change. i

What is claimed is:

1. In a process for producing a flame-resistant foam composition by thereaction of (1) a polyarylpolyisocyanate having at least twointerconnected aromatic rings substituted with at least one isocyanatogroup per aromatic ring, (2) a polyfunctional aromatic carboxylic acidderivative comprising an aromatic nucleus substituted by carbonyl-basedmembers selected from the group consisting of anhydride, carboxyl, andacyl halide, and (3) a carboxy-containing adduct polyol or mixture ofadduct 1 polyols prepared by reacting (a) at least one polyether polyolwith (b) an anhydride of a polyfunctional carboxylic acid at atemperature between 150 F. and 350 F., the improvement comprising thecarrying out of the foaming reaction in the presence of a catalyticamount of antimony tallate.

2. The process of claim 1 wherein a poly (ethylene glycol) is added tothe carboxy-containing polyol.

10 References Cited UNITED STATES PATENTS 9/1971 Papa 260 2.5 AB 1/1972Kus 2602.5 AM 4/1966 Hindersinn 2602.5AB 2/1972 Marcus 252-182 FOREIGNPATENTS 9/ 1971 Great Britain. 4/1966 Belgium.

DONALD E. CZAJA, Primary Examiner C. W. IVY, Assistant Examiner US. Cl.X.R.

2602.5 AM, 2.5 AN, 2.5 AV, 75 NB, 77.5 AB

